My first guess is that the client works because you use "localhost"
while slurpd doesn't because you use a fully qualified name, and (a)
the name may not resolve to the right host, or (b) the slave might not
be listening on the appropriate listener, e.g. it was started with -h
"ldap://localhost:9389&quot; or anything like that.

Indeed ! I knew it should be something silly ... Now I start my slave
this way:
-h '"ldap://calaz.int-evry.fr:9389/ ldaps://calaz.int-evry.fr:9636/"
and it's OK ;-), thanks !.